LRS Wavelength Calibration

LRS grism 1
300 l/mm, ~4.5 Å/pix, 4000-10500 Å
Region Gif Image PS Image
Ne lamp
Cd lamp
sky lines
IRAF Compatible Line List | IRAF Identify Output

LRS grism 2
600 l/mm, ~2.5 Å/pix, 4300-7300 Å
Region Gif Image
4300-5500 Å
5500-7300 Å
Bright Lines
IRAF Compatible Line List | IRAF Identify Output

LRS grism 3 now defunct
holographic grating, 1.9 Å/pix, 6250-9100 Å
Region Gif Image
Ne wavelength extraction
Ne pixel extraction
IRAF Compatible Line List | IRAF Identify Output

NOTE: We no longer have the HgCdZn lamp which has been replaced with a Cd lamp.

The previous line lists and plots were generated in an iterative manner. Night sky lines were first used to identify the bright lines in the HgCdZn and Ne spectra independently. The HgCdZn and Ne plots were then added and the previously identified lines were used to make further identifications. A comparison with Keck LRIS line lists was then performed to improve confidence in the identifications. We now believe all plotted lines to be correct identifications, but some small uncertainty remains in the far red end (>9000 Å), so use these identifications at your own risk. Feedback is always welcome.

We have determined the standard fit to be a 5th order Chebyshev polynomial (6 coefficients). Though basically a standard polynomial it is rumored that the Chebyshev form, in the presence of noise, fits the underlying function more precisely. Though most spectrographs do not show the red turn over we observe, we believe that this is a consequence of the unusually large range of angles of light exiting the grating.

Finally, all data represented below was acquired with the LRS set to observe the highest resolution possible with a given grism. We used the 0.5 arc-second pinholes illuminated by the comparison lamps. This should give the user and idea of which lines are likely to be blended. Only additive error effects were taken into account in the data reduction. No flat fielding, illumination correction, or photometric calibration was performed.